more

mp3/src/servers/coordinator.go

@@ -96,7 +96,11 @@ func (host *Server) LockAccount(key string, ltype string) bool {
 		acc.Upgrade.Lock()
 		acc.RW.RLock()
 		acc.Upgrade.Unlock()
+		
+		acc.ReaderLock.Lock()
+		acc.Readers++
 		acc.LockType = "R"
+		acc.ReaderLock.Unlock()
 
 		// fmt.Println("Couldnt get lock after 50 attempts.")
 	} else {
@@ -122,6 +126,7 @@ func (host *Server) LockAccount(key string, ltype string) bool {
 		acc.Upgrade.Lock()
 		acc.RW.Lock()
 		acc.Upgrade.Unlock()
+
 		acc.LockType = "W"
 
 		// fmt.Println("Couldnt get lock after 50 attempts.")
@@ -177,12 +182,24 @@ func (host *Server) Release(account string, commit bool) bool {
 
 		// Read Lock
 		if acc.LockType == "R" {
-			acc.LockType = ""
+			acc.ReaderLock.Lock()
+			acc.Readers--
+			if acc.Readers == 0 {
+				acc.LockType = ""
+			}
+			acc.ReaderLock.Unlock()
 			acc.RW.RUnlock()
 
 			// Write Lock
 		} else {
-			acc.LockType = ""
+			acc.ReaderLock.Lock()
+			if acc.Readers == 0 {
+				acc.LockType = ""
+			} else {
+				acc.LockType = "R"
+			}
+
+			acc.ReaderLock.Unlock()
 			acc.RW.Unlock()
 		}
 
@@ -528,7 +545,7 @@ func (host *Server) withdraw(operation Client_msg) {
 			val.Balance -= operation.Amount
 			host.Tr.Accounts[local_key] = val
 
-			// Lock not "W", need upgrade
+		// Lock not "W", need upgrade
 		} else {
 			// Local upgrade
 			if operation.Branch == host.Id {
@@ -537,14 +554,14 @@ func (host *Server) withdraw(operation Client_msg) {
 				val.LockType = "W"
 				host.Tr.Accounts[local_key] = val
 
-				// Remote upgrade
+			// Remote upgrade
 			} else {
 				req_out.Request = "UPGRADE"
 				go host.server_write(operation.Branch, req_out)
 
 				resp_in := <-host.Trans_chan
 				if resp_in.Status {
-					val.Balance += operation.Amount
+					val.Balance -= operation.Amount
 					val.LockType = "W"
 					host.Tr.Accounts[local_key] = val
 				} else {
@@ -646,7 +663,7 @@ func (host *Server) balance(operation Client_msg) {
 			host.abort()
 			return
 
-			// Else grab read lock
+		// Else grab read lock
 		} else {
 			realAcc := cast.(*Account)
 
@@ -770,6 +787,7 @@ func (host *Server) commit() {
 
 			// POSSIBLE TIMING ISSUE IF FUNCTION ENDS WHILE STILL WAITING ON CHANNEL RESPONSES
 			go host.server_write(data.Branch, msg_out)
+			
 		}
 	}
 

mp3/src/servers/server.go

@@ -74,6 +74,7 @@ type Account struct{
 	LockType string 	  // "R" or "W"
 	Readers  int
 	Committed bool		  // True if account has new, but uncommitted - May need to add conditional wait 
+	ReaderLock *sync.Mutex
 }
 
 // type Msg struct{ // For testing